A pressing need exists for a dosage form for administering to human females for contraception an estrogen and a progestogen at a rate controlled by the dosage form. The need existed since early 1960 when oral contraceptive pills comprising an estrogen and a progestogen became available for contraception. The contraceptive pills used by the prior art delivered the estrogenic and the progestational steroids in tablet form, that is, in a bulk, nonrate controlled amount. The contraceptive steroids were delivered heretofore unprotected from the changing environment of the gastrointestinal tract and with little consideration for the pharmacological and the physiological needs of the recipient. The contraceptive steroids were delivered by the prior art as an oral pill devoid of rate controlled delivery because contraceptive steroids are practically insoluble in aqueous media. Thus, the steroids do not lend themselves for manufacture into a dosage form that administers the steroids at a controlled and known rate per unit time.
In light of the above presentation it will be appreciated by those having skill in the dispensing art to which this invention pertains that a pressing need exists for a dosage form that can deliver to a recipient at a controlled rate in a known amount per unit time the valuable estrogen and progestogen for contraception. The pressing need exists for an oral dosage form that can deliver estrogen and progestogen simultaneously at controlled rate in substantially constant doses per unit time over a prolonged period of time for their contraceptive effects, and substantially independent of the variable environment of the gastrointestinal tract. It will be further appreciated by those skilled in the contraceptive art that such a novel and unique dosage form that can administer the two contraceptive steroids in rate-controlled doses over time and, simultaneously, provide contraception would represent an advancement and a valuable contribution to the art.